Bituminous binders may be either anhydrous bituminous binders or bituminous emulsions. The latter are prepared by dispersing anhydrous bituminous binders in an aqueous phase, in the presence of emulsifiers.
Polymer-bitumen binders may be cross-linked, conventionally by means of sulphur or derivatives thereof.
“Road” bituminous binders fulfil their binding function in:                “hot coated materials” obtained by the hot mixing of anhydrous bituminous binders with aggregates, these mixtures then being spread on the roadway in order to form road surfaces;        “surface coatings with anhydrous binders” obtained by hot spreading on the roadway first of all of an emulsion of bituminous binders and mixed aggregates;        “cold coated materials” obtained by the cold mixing of bituminous emulsions with aggregates, these mixtures then being spread on the roadway in order to form road surfaces;        or “surface coated materials with bituminous emulsions” obtained by the cold spreading on the roadway first of all of bituminous emulsions and mixed aggregates.        
These coated materials or coatings must first of all form a homogenous mixture comprising a bituminous matrix and aggregates dispersed in this matrix. The rheology of this mixture must be suited to the application on roadways to form a road surface.
Once applied, these coated materials or coatings must next increase in cohesion in order to be transformed into a road surface provided with the expected durable mechanical properties.
Heating; putting in emulsion and/or fluxing (or fluidification) by means of bitumen solvents (fluxes are means normally used for obtaining the consistency suitable for the application.
The heating and use of fluxes of petroleum origin containing volatile organic compounds (VOCs) have negative environmental repercussions.
An improvement has been made to fluidification by fluxing through EP 900822 B1, which proposes fluxes for bituminous binders consisting of one or more methyl monoesters of C16-C18 fatty acids, in particular sunflower oil, linseed oil and/or isomerised sunflower oil.
The purpose of modifying bitumens by means of polymers is in particular to improve thermal resistance, cohesion, elongation capacity, viscoelastic characteristics and passive adhesive strength (better resistance to decoating on the roadway) of the hardened bituminous surfaces. These polymer-bitumens are used both for anhydrous coating materials/coatings and for coated materials/coatings comprising emulsions.
The modification of bitumens by polymers is therefore now unavoidable, but is not without problems in terms of manufacture. This is because polymer-bitumen binders are obtained by the gradual addition of a polymer to a bitumen, hot, in a mechanical grinder/dispersing machine. This operation, the purpose of which is to disperse the polymer in the bitumen, is difficult to perform. It requires the use of a specific grinder/dispersing machine, of high performance and very expensive. It also requires long periods of dispersion/grinding, for example 1 to 3 hours.
To facilitate this operation and to obtain better dispersion, use of a counting oil such as an oil of petroleum, plant or mineral origin, for example at the rate of 3% to 7% by weight with respect to the bitumen, is known.
This manufacture of polymer-bitumen therefore requires an infrastructure that is not only a problem on an economic level but also has an environmental impact.
Since it is not possible to increase the number of such infrastructures and having regard to the cost of transporting these polymer-bitumen compositions, primary polymer-bitumen mixtures with a concentration of polymer have been developed.
FR 2951188 B1 thus discloses a polymer-bitumen mother solution free from oil of undesirable petroleum origin but rather comprising at least one oil of plant and/or animal origin, at least 20% by weight of polymer, with respect to the weight of the mother solution, with or without at least one cross-linking agent. This oil of plant and/or animal origin is acidic and its acid value measured in accordance with NF EN ISO 660 is between 50 and 300 mg KOH/g, for example between 140 and 196 mg. It is chosen from fatty acids of tall oil or rapeseed oil, taken alone or in a mixture.
According to FR 2951188 B1, the mother solution in question has a very high polymer concentration. In contradiction, it is however indicated in FR 2951188 B1 that “the mother solution according to the invention preferably comprises at least 50% by weight of polymer”, and in the following paragraph this concentration of polymer is “preferably from 20% to 50% by mass of polymer, with respect to the mass of the mother solution, preferably from 25% to 45%, more preferentially from 30% to 40%, even more preferentially from 32% to 35%, and this without any phenomenon of gelling during preparation and/or storage thereof”. With respectively 25% and 40% by mass of polymer, the examples in FR 2951188 B1, SM5 SM5bis on the one hand and SM6 SM6bis on the other hand are therefore situated in the second “preference”.
It therefore appears that the objective of FR 2951188 B1, which is to obtain a polymer-bitumen mother solution with a very high concentration of polymer, is not actually achieved.
WO 02/10285 describes dry liquid concentrates intended to be mixed with bitumens and containing granulates of rubber (55%-95%) and tall oil (45%-5%).
The polymer/plant oil mixtures of the prior art can be improved, in particular in terms of use and impact on the physical and chemical properties of the polymer-bitumens in which they are incorporated.